In order to realize safe vehicle motion, apparatus for automatically controlling steering of a vehicle, accelerator, and brakes have been researched and developed by detecting dangerous events around the vehicle so as to avoid the detected dangerous events. Some vehicles are already equipped with such apparatus. Among them, a system which detects white lines and road shoulders by sensors installed in the vehicle and which, when there is a danger that the vehicle will run off the lane or road, alerts the driver and a system that controls the vehicle speed or direction of motion by automatic brake control or by automatic steering control are effective in preventing road departure accidents.
In preventing the vehicle from running off the lane, a system is put into practical use which detects a white line using an in-vehicle monocular camera or stereo camera and which alerts the driver when the vehicle runs off the lane from the positional relationship between the detected white line and the vehicle. Furthermore, regarding a system which detects a white line by an in-vehicle camera and which controls the steering of the vehicle in a case where the vehicle is about to run off the lane from the positional relationship between the detected white line and the vehicle, there is much patent literature.
Furthermore, an apparatus for detecting a three-dimensional object on a road shoulder such as a guardrail by means of a stereo camera is shown in patent literature 1. Use of this system makes it possible to alert the driver or control the steering in a case where the vehicle is likely to collide with the three-dimensional object on the road shoulder, even if there is no white line.
Further, patent literature 2 sets forth an apparatus that detects a gutter in a road shoulder using an in-vehicle monocular camera. Here, the gutter is detected by making use of the fact that motion on a road surface is different from portions located at positions lower than the road surface using brightness information of an image from the monocular camera.